As is known, human perspiration occurs by expelling sweat through the pores of the skin, each pore being connected to sweat glands.
The generated sweat is liquid, and once it has come into contact with the warm skin it evaporates, removing its own latent heat of evaporation (approximately 580 calories/g at 30° C.).
This cools the skin and activates the phenomenon of body thermoregulation.
It is rather simple to deduce, therefore, that ventilation and vapor permeability of items of clothing are key factors in the dissipation of the metabolic heat of the body.
Currently there are no methods and devices for measuring the vapor permeability of items of clothing such as jackets or trousers which take into consideration the entire item.
Currently known methods are in fact limited exclusively to the component materials, allowing to obtain data related to vapor permeability defined in milligrams per square centimeter per hour or in grams per square centimeter per day, but do not take into consideration the actual structure of the item.
Therefore, in practice there are no methods for determining simply the amount of water vapor or more generally the amount of humidity that is present within a complete item of clothing.